In a conventional medical check-up or diagnosis of a disease state, several cc, a large amount of blood has heretofore been sampled from a patient, and the diagnosis has been carried out in accordance with measured values obtained by a large-scaled automatic blood analysis apparatus. Usually, this automatic analysis apparatus is large in size, and therefore is installed in a medical institution such as a hospital. Further, the apparatus is operated only by a person who has specialty qualification.
However, in recent years, there is increased a demand to develop a new device enable to grasp a health condition of a patient quickly and put such device to practical use. To the device, a fine working technique for use in preparing an extremely advanced semiconductor device is applied, analysis devices such as various sensors are arranged on a chip having a size of a several mm to several cm square at most, and a body fluid such as blood of a person being tested is applied to the device. By development of such inexpensive device, daily health cares of aged people could be managed at home in a coming aging society, and accordingly a health insurance benefit tracing a course to an increase would be compressed. Such device may realize quick diagnosis of presence of an infectious disease (hepatitis, acquired immune deficiency syndrome, etc.) of the person being tested and proper action thereafter in the field of the emergency medical care. Thus, various social effects could be expected, and therefore the device is in a technical field which has gotten a lot of attention. In this situation, in lieu of the conventional automatic analysis apparatus, there have been developed a small-sized simple blood analysis method and blood analysis device for personally performing blood analysis at home (e.g., Unexamined Japanese Patent Publication (KOKAI) JP 2001-258868 A; corresponding to WO 01/69242 A1 and US 2003/0114785 A1)).
FIG. 1 shows one example of a blood analysis device formed as a micro module described in JP 2001-258868 A. Reference numeral 101 denotes a lower substrate of the blood analysis device, and a micro trench channel (microcapillary) 102 is formed on the lower substrate by etching. An upper substrate (not shown) having a substantially equal size is laminated onto the lower substrate 101 to seal the trench channel 102 from the outside.
In the flow channel 102, blood sampling means 103, plasma separating means 104, analysis means 105, and moving means 106 are successively disposed from a most upstream portion toward a most downstream portion. A hollow blood collecting needle 103a is attached to the blood sampling means 103 which is provided on a most upstream end portion of the flow channel. A human body is stung with the needle 103a so that the needle constitutes an intake port of the blood into the substrate. The separating means 104 is formed by bending the flow channel 102 midway, and is constituted of, for example, a U-shaped microcapillary. After introducing the sampled blood into this U-shaped microcapillary, acceleration is applied to the substrate in a certain direction by a centrifuge, blood cell components are precipitated in a U-shaped lowermost portion, and a plasma is separated as a supernatant. The analysis means 105 includes sensors for measuring a pH value, and concentration of each of oxygen, carbon dioxide, sodium, potassium, calcium, glucose, lactic acid and the like in the blood.
The moving means 106 positioned in the most downstream portion of the flow channel moves the blood within the microcapillary by an electro-osmosis flow, and is constituted of electrodes 107, 108 and a flow channel portion 109 connecting both electrodes. A buffer solution with which the flow channel is filled previously is moved into the downstream side of the flow channel by the electro-osmosis flow generated by application of a voltage between the electrodes. And the blood is taken into the substrate from the blood sampling means 103 disposed at the front end of the channel 102 by a generated suction force. The plasma obtained by centrifugal separation is fed into the analysis means 105.
Reference numeral 110 denotes output means for taking information out of the analysis means, and comprises electrodes and the like, and 111 is control means for controlling the above-described sampling means, plasma separating means, analysis means, moving means, and output means, as needed.
The blood collected by the sampling means 103 is separated into plasma and blood cell components by the separating means 104, and the plasma is transferred into the analysis means 105. Then, the pH value in the plasma, and the respective concentrations of oxygen, carbon dioxide, sodium, potassium, calcium, glucose, lactic acid and the like in the plasma are measured. The movement of the blood between the respective means is performed by the moving means 106 having a pump function such as means using phenomena like electrophoresis and electro-osmosis. In FIG. 1, a downstream region of the flow channel 102 is branched into five, and each branch is provided with the analysis means 105 and moving means 106.
A glassy material such as quartz has been often used in the substrate of the blood analysis device, but, in recent years, a resin material has been regarded as more suitable for mass-producing the apparatuses at reduced costs, and used as a disposable material.
In the conventional blood analysis device shown in FIG. 1, when a blood sample is introduced into the device, the moving means like an electro-osmosis pump 106 is required. After centrifugally separating the introduced blood together with the substrate to obtain the plasma, the electro-osmosis pump 106 needs to be operated again in order to move this plasma to the analysis means 105. Especially when the analysis means is a sensor constituted based on an electrochemical principle, this sensor should be calibrated beforehand using a calibrator solution. Specifically, this sensor is immersed in the calibrator solution to calibrate the sensor before introducing the plasma into the sensor. After the calibration, the calibrator solution has to be discharged from the analysis means. The moving means like the pump is required also in transferring such calibrator solution.
Possible moving means for use is the electro-osmosis pump disposed in the same substrate as shown in FIG. 1, or a negative-pressure pump installed outside the substrate. By these moving means, the blood, the plasma, the calibrator solution and the like are fed under pressure, or sucked and moved. In this case, a suction force or the like of the movement means needs to be precisely controlled in order to move a desired liquid to a desired position in the blood analysis device. For this purpose, a position sensor for the liquid has to be newly installed in the inside or the outside of the blood analysis device, and there has been a problem that the device becomes expensive because such control mechanism or position sensor is added.
When the analysis means is the sensor constituted based on the electrochemical principle, the sensor is calibrated with a calibrator solution (standard solution) containing a component to be tested having a known concentration, and the calibrator solution has to be thereafter discharged from the analysis means. However, even when the calibrator solution is discharged, a slight amount of calibrator solution remains on the surface of the analysis means or flow channel means in accordance with wettability of the surface. As described above, in the blood analysis device which is the present object, sizes of means constituting devices like the flow channel means are reduced in such a manner as to analyze concentrations of various chemical substances in a small amount of several microliters of blood. In general, when a size of an object decreases, a ratio S/V of a surface area (S) to a volume (V) increases, and this means that the surface effect remarkably appears. Accordingly, even when the amount of the calibrator solution remaining on the surface of the flow channel or analysis means is small, the analysis device having a less amount of introduced plasma has a problem that the measured concentrations of the chemical substances are fluctuated. Therefore, after the calibration, the calibrator solution needs to be reliably discharged from the analysis means before the plasma is introduced into the analysis means.
The present invention has been developed in view of such situations, and a first object is to provide a blood analysis device which separates a plasma by a centrifugal operation in a flow channel and which can convey blood, plasma, and calibrator solution without using any pump or the like in the device and which more reliably discharges the calibrator solution from a sensor section so that high-precision analysis is possible.
Moreover, a second object of the present invention is to provide a blood analysis method in which blood, plasma, and calibrator solution can be conveyed only by a centrifugal operation in a blood analysis device in using the apparatus for separating the plasma in the flow channel by the centrifugal operation and which reliably discharges the calibrator solution from a sensor section so that high-precision analysis is possible.